The present invention relates to an automatic transmission system for vehicles, which comprises a clutch and a gear-type transmission.
In the prior art automatic transmission system including a clutch and a gear transmission, if at the time the vehicles is stopped the selector is in, for example, the "D" position, the transmission is shifted to the first gear position, while the mechanical clutch, (which may be a dry-type single-disc friction clutch, for example), is put in the disengaged state, and the disengaged state of the mechanical clutch is maintained until the accelerator pedal is depressed for vehicle starting. As a result, in this case, the clutch release bearing continues to rotate at the same speed as the engine so long as the vehicle remains stopped, remarkedly shortening the service life of the clutch release bearing.
To eliminate this disadvantage, there has been proposed an automatic transmission control system in which the transmission is shifted to its neutral position and the condition of the clutch is returned to the engaged state regardless of the position of the selector when the clutch has remained in the disengaged state for more than a predetermined time. However, in this proposed system, if the ignition switch is turned off in the case where the selector is in a position other than the "N" but the transmission has been shifted to neutral and the clutch has been engaged in order to prevent the clutch release bearing from wearing, the actual gear position and the selected position of the selector will no longer match. This disadvantageous state may also occur if the ignition switch is turned off before the transmission has been shifted to the set position during he gear shift operation. The state where the actual gear position does not match with the selected position of the selector may be dangerous, especially when the driver parks the vehicle with the gear in a position other than neutral on the assumption that the selected gear position is the actual gear position.